Question

Write a program to sum a series of numbers entered by the user. The program should first prompt the user for how many numbers are to be summed. The program should then prompt the user for each of the numbers in turn and print out a total sum after all the numbers have been entered. Hint: Use an input statement in the body of the loop.

Short answer

A loop sums user-input numbers, outputs the total sum.

Step-by-step solution

Initialize Variables

Start by initializing a variable to store the total sum of the numbers. Let's call this variable `total_sum` and set it to 0. Also, declare a variable to store the number of inputs, such as `number_of_inputs`.

Prompt User for Number of Entries

Use an `input` statement to ask the user how many numbers they would like to sum. Convert this input to an integer and assign it to the `number_of_inputs` variable.

Create Loop for User Inputs

Set up a `for` loop or a `while` loop that iterates, prompting the user to enter a number each time. Make sure the loop runs exactly `number_of_inputs` times.

Update Sum Inside the Loop

Inside the loop, use an `input` statement to get each number from the user. Convert each input to an integer, then add it to the `total_sum` variable.

Output Final Sum

Once the loop has completed, print out the `total_sum` to display the result to the user.

Key concepts

Loops

In Python programming, loops are used to execute a block of code repeatedly, allowing you to perform tasks efficiently without writing repetitive code.
There are two main types of loops in Python: **for** loops and **while** loops. Generally, loops are perfect for tasks like iterating over a sequence (like a list or a string), or running a block of code a certain number of times.

**For Loops**: - Used when you have a predefined sequence or range. For example, iterating over a list of numbers from 0 to 9. - Utilizes the `range()` function for numerical sequences: `for i in range(10):` **While Loops**: - Continue running as long as a condition is **True**. These loops require careful condition handling to prevent infinite loops. - Example: `while flag == True:`

In the context of summing user-entered numbers, we can use a loop to ensure the program asks the user for input multiple times, based on how many numbers the user wants to sum. This is efficient and limits user errors in input.

User Input

User input is a way to make programs interactive. In Python, you'll often use the `input()` function to take data from the user. This function helps gather input as strings, which you can then convert into appropriate data types like integers or floats.
Gathering user input is crucial in creating dynamic applications. Let's break down its usage:

- **Input Collection**: To prompt a user for input, you can execute something like `input("Enter a number: ")`. This displays a message and waits for user input. - **Data Conversion**: Since `input()` returns a string, it is often necessary to convert the result to another type, such as an integer: `int(input())`.

For our exercise, using `input()` to retrieve the series of numbers from the user, and converting these inputs into integers, is necessary for calculating the sum. This step ensures users provide the correct data format needed for processing.

Variables

Variables are containers for storing data values. They act as a storage place in the program where you can hold information to manipulate or display later.
Variables can hold different data types, including integers, floats, strings, and more. In Python, variable names should be meaningful and descriptive, making your code easier to read and understand.

Key aspects of variables include: - **Initialization**: Before using a variable, you must initialize it. For instance, setting `total_sum` to 0 ensures we start with a neutral value. - **Assignment**: At various points in your program, you may need to update a variable's value, such as adding a number to our total sum during each iteration of a loop. - **Manipulation**: You can manipulate variables' values using operators, which is what happens when you're adding each user's input to our `total_sum`.

In the task of summing numbers, variables store both the total sum and the number of inputs, serving as placeholders and counters that guide the logic flow of your program.